This invention relates to video display line generators and particularly to video line generators which are randomly or sequentially addressable for use in a flat image display device.
A flat image display device has several advantages over the prior art electron beam scanning devices such as the cathode ray tube. A significant advantage is the relative compactness of the flat image display device.
Conventional television picture tubes comprise an elongated glass envelope having a phosphor coated faceplate at one end and an electron gun at the other end for generating a focused beam of electrons toward the phosphor screen. An elongated structure is required to accommodate the electron gun and deflection system. Consequently, in order to preserve linearity and definition of the display, an increase in the size of the display screen must be accompanied by an increase in the depth of the tube. As a result, a large display screen, for example 3' .times. 4', would require a beam scanning tube of unmanageable bulk for most practical purposes.
In addition, prior art cathode ray tube devices are inherently suitable for scanning in a substantially sequential manner precluding random addressing on a line-at-a-time basis. This limitation impairs the versatility of such devices as well as their efficiency of operation in response to a randomly addressed inputs as might be involved in a memory or storage tube or a specialized display application.
One significant drawback associated with flat image display devices relates to the addressing or scanning capability. In conventional beam scanning television tubes, vertical scanning of the standard 524 lines can be accomplished using a small number of leads connected to the deflection system. In a line or area cathode device of the type suitable for flat image displays, as many as 524 leads may be required just to accomplish the vertical scanning. This becomes a problem since bringing out a minimum of 524 leads through a vacuum seal is not a trivial matter.
One way of reducing the number of leads required for line-at-a-time addressing in a flat image display device is to employ dynodes having digitally coded electrodes thereon for applying electron accelerating and repelling potentials, see for example U.S. Reissue Patent No. 27,520 issued to Hultberg, et al. One disadvantage of this approach is that the digital coding makes each dynode member unique; consequently, a device for scanning 512 lines would require several different dynode members. As a result, the minimum number of dynode members will be dictated, in most practical applications, by the digital coding and not by the electron emission characteristics of the materials selected.